I recently switched my main workstation at home to f16. Since then, rpc.idmapd does not properly pick set the idmapping domain at boot time. If I go in after booting and do a "service nfs-idmap restart" then it will work properly. It also works properly if I set the domain explicitly in /etc/idmap.conf. I suspect the problem is a boot-time ordering issue. rpc.idmapd is likely being started before the hostname is properly set on the machine. I'm not sure exactly how to fix this -- we may need some systemd expertise. In any case -- perhaps it's time to move to the new idmapper anyway?
*** This bug has been marked as a duplicate of bug 748275 ***